Angular distance between the plumb line at a station and the plane of the celestial equator It is the latitude which results directly from observations of celestial bodies, uncorrected for deflection of the vertical which, in the United States, may amount to as much as 25'. Astronomical latitude applies only t

Related Terms

RESTRICTOR

A device for producing a deliberate pressure drop or resistance in a line by reducing the cross-sectional flow area.

SPREAD

The divergence of the air stream in a horizontal or vertical plane after it leaves the outlet.

MOMENT OF INERTIA

The quantity obtained by multiplying the mass of each small part of a body by the square of its distance from an axis, and adding all the results.

GREENWICH HOUR ANGLE

Angular distance west of the Greenwich celestial meridian; the arc of the celestial equator, or the angle at the celestial pole, between the upper branch of the Greenwich celestial meridian and the hour circle of a point on the celestial sphere, measured westward from the Greenwich celestial meridian throug

GRID RHUMB LINE

A line making the same oblique angle with all grid meridians. Grid parallels and meridians may be considered special cases of the grid rhumb line.

HAND LEAD

A light sounding lead (7 to 14 pounds), usually having a line of not more than 25 fathoms

HARPOON LOG

A log which consists of a rotator and distance registering device combined in a single unit, which is towed through the water. The TAFFRAIL LOG is similar except that the registering device is located at the taffrail, with only the rotator in the water.

GROUND LOG

A device for determining the course and speed over the ground in shallow water consisting of a lead or weight attached to a line. The lead is thrown overboard and allowed to rest on the bottom. The course over ground is indicated by the direction the line tends and the speed by the amount of line paid out in a unit of time.

GYROSCOPIC DRIFT

The horizontal rotation of the spin axis of a gyroscope about the vertical axis

HEAVE

The oscillatory vertical rise and fall, due to the entire hull being lifted by the force of the sea. Also called HEAVING

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